1. Field of the Invention
The present invention relates to sealing devices and more particularly, to seals, packings and the like used in environments wherein at least a portion of the sealing device is subjected to extrusion forces.
Sealing devices such as seals or packings, whether of the dynamic or static type, are usually made, or have portions made, of materials which, to some extent, are resilient or at least flexible or deformable. In order to seal effectively, it is necessary that the sealing device be placed under some compressive loading between the components of the assembly to be sealed. Then, if the seal is subjected to a sufficient pressure in use, extrusion forces are set up which tend either to distort the seal and impair its effectiveness as such, or in more severe cases, for force portions of the seal into clearances between the components to be sealed.
2. Description of the Prior Art
One attempted solution to this problem has been to use separate rigid backup members such as washers in conjunction with the seals or packings. However, for various reasons, including simplification, effectiveness, minimizing of the space needed to accommodate these members, etc., it is usually more desirable to use an integral seal or packing.
Accordingly, other efforts have been directed at providing sealing devices having anti-extrusion elements integrally affixed to the more deformable or flexible portion thereof. In some cases, the anti-extrusion elements have been coil springs or other solid metal bodies. In such devices, the flexible portion of the seal sometimes extrudes over or past the anti-extrusion element due either to failure of the latter in service or to undetected manufacturing defects. It is believed that these problems may have been at least partially due to the relatively drastic difference in the rigidity of the two portions of such devices.
In other instances, the anti-extrusion sections of the sealing devices have been comprised of materials which, while not as readily deformable as the sealing portions of devices, are not as rigid as the metal bodies described above. Examples of such devices are shown in U.S. Pat. Nos. 3,094,337 and 3,719,366. However, when such devices are subjected to extremely high temperatures and/or pressures, the anti-extrusion elements themselves may become somewhat deformed by the extrusion forces.